This file is indexed.

/usr/lib/python3/dist-packages/pydot.py is in python3-pydot 1.0.28-2.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

   1
   2
   3
   4
   5
   6
   7
   8
   9
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  24
  25
  26
  27
  28
  29
  30
  31
  32
  33
  34
  35
  36
  37
  38
  39
  40
  41
  42
  43
  44
  45
  46
  47
  48
  49
  50
  51
  52
  53
  54
  55
  56
  57
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74
  75
  76
  77
  78
  79
  80
  81
  82
  83
  84
  85
  86
  87
  88
  89
  90
  91
  92
  93
  94
  95
  96
  97
  98
  99
 100
 101
 102
 103
 104
 105
 106
 107
 108
 109
 110
 111
 112
 113
 114
 115
 116
 117
 118
 119
 120
 121
 122
 123
 124
 125
 126
 127
 128
 129
 130
 131
 132
 133
 134
 135
 136
 137
 138
 139
 140
 141
 142
 143
 144
 145
 146
 147
 148
 149
 150
 151
 152
 153
 154
 155
 156
 157
 158
 159
 160
 161
 162
 163
 164
 165
 166
 167
 168
 169
 170
 171
 172
 173
 174
 175
 176
 177
 178
 179
 180
 181
 182
 183
 184
 185
 186
 187
 188
 189
 190
 191
 192
 193
 194
 195
 196
 197
 198
 199
 200
 201
 202
 203
 204
 205
 206
 207
 208
 209
 210
 211
 212
 213
 214
 215
 216
 217
 218
 219
 220
 221
 222
 223
 224
 225
 226
 227
 228
 229
 230
 231
 232
 233
 234
 235
 236
 237
 238
 239
 240
 241
 242
 243
 244
 245
 246
 247
 248
 249
 250
 251
 252
 253
 254
 255
 256
 257
 258
 259
 260
 261
 262
 263
 264
 265
 266
 267
 268
 269
 270
 271
 272
 273
 274
 275
 276
 277
 278
 279
 280
 281
 282
 283
 284
 285
 286
 287
 288
 289
 290
 291
 292
 293
 294
 295
 296
 297
 298
 299
 300
 301
 302
 303
 304
 305
 306
 307
 308
 309
 310
 311
 312
 313
 314
 315
 316
 317
 318
 319
 320
 321
 322
 323
 324
 325
 326
 327
 328
 329
 330
 331
 332
 333
 334
 335
 336
 337
 338
 339
 340
 341
 342
 343
 344
 345
 346
 347
 348
 349
 350
 351
 352
 353
 354
 355
 356
 357
 358
 359
 360
 361
 362
 363
 364
 365
 366
 367
 368
 369
 370
 371
 372
 373
 374
 375
 376
 377
 378
 379
 380
 381
 382
 383
 384
 385
 386
 387
 388
 389
 390
 391
 392
 393
 394
 395
 396
 397
 398
 399
 400
 401
 402
 403
 404
 405
 406
 407
 408
 409
 410
 411
 412
 413
 414
 415
 416
 417
 418
 419
 420
 421
 422
 423
 424
 425
 426
 427
 428
 429
 430
 431
 432
 433
 434
 435
 436
 437
 438
 439
 440
 441
 442
 443
 444
 445
 446
 447
 448
 449
 450
 451
 452
 453
 454
 455
 456
 457
 458
 459
 460
 461
 462
 463
 464
 465
 466
 467
 468
 469
 470
 471
 472
 473
 474
 475
 476
 477
 478
 479
 480
 481
 482
 483
 484
 485
 486
 487
 488
 489
 490
 491
 492
 493
 494
 495
 496
 497
 498
 499
 500
 501
 502
 503
 504
 505
 506
 507
 508
 509
 510
 511
 512
 513
 514
 515
 516
 517
 518
 519
 520
 521
 522
 523
 524
 525
 526
 527
 528
 529
 530
 531
 532
 533
 534
 535
 536
 537
 538
 539
 540
 541
 542
 543
 544
 545
 546
 547
 548
 549
 550
 551
 552
 553
 554
 555
 556
 557
 558
 559
 560
 561
 562
 563
 564
 565
 566
 567
 568
 569
 570
 571
 572
 573
 574
 575
 576
 577
 578
 579
 580
 581
 582
 583
 584
 585
 586
 587
 588
 589
 590
 591
 592
 593
 594
 595
 596
 597
 598
 599
 600
 601
 602
 603
 604
 605
 606
 607
 608
 609
 610
 611
 612
 613
 614
 615
 616
 617
 618
 619
 620
 621
 622
 623
 624
 625
 626
 627
 628
 629
 630
 631
 632
 633
 634
 635
 636
 637
 638
 639
 640
 641
 642
 643
 644
 645
 646
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656
 657
 658
 659
 660
 661
 662
 663
 664
 665
 666
 667
 668
 669
 670
 671
 672
 673
 674
 675
 676
 677
 678
 679
 680
 681
 682
 683
 684
 685
 686
 687
 688
 689
 690
 691
 692
 693
 694
 695
 696
 697
 698
 699
 700
 701
 702
 703
 704
 705
 706
 707
 708
 709
 710
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
# -*- coding: Latin-1 -*-
"""Graphviz's dot language Python interface.

This module provides with a full interface to create handle modify
and process graphs in Graphviz's dot language.

References:

pydot Homepage: http://code.google.com/p/pydot/
Graphviz:       http://www.graphviz.org/
DOT Language:   http://www.graphviz.org/doc/info/lang.html

Programmed and tested with Graphviz 2.26.3 and Python 2.6 on OSX 10.6.4

Copyright (c) 2005-2011 Ero Carrera <ero.carrera@gmail.com>

Distributed under MIT license [http://opensource.org/licenses/mit-license.html].
"""

from __future__ import division, print_function

__author__ = 'Ero Carrera'
__version__ = '1.0.29'
__license__ = 'MIT'

import os
import re
import subprocess
import sys
import tempfile
import copy

from operator import itemgetter

try:
    import dot_parser
except Exception:
    print("Couldn't import dot_parser, loading of dot files will not be possible.")


PY3 = not sys.version_info < (3, 0, 0)

if PY3:
    NULL_SEP = b''
    basestring = str
    long = int
    unicode = str
else:
    NULL_SEP = ''


GRAPH_ATTRIBUTES = set([
    'Damping', 'K', 'URL', 'aspect', 'bb', 'bgcolor',
    'center', 'charset', 'clusterrank', 'colorscheme', 'comment', 'compound',
    'concentrate', 'defaultdist', 'dim', 'dimen', 'diredgeconstraints',
    'dpi', 'epsilon', 'esep', 'fontcolor', 'fontname', 'fontnames',
    'fontpath', 'fontsize', 'id', 'label', 'labeljust', 'labelloc',
    'landscape', 'layers', 'layersep', 'layout', 'levels', 'levelsgap',
    'lheight', 'lp', 'lwidth', 'margin', 'maxiter', 'mclimit', 'mindist',
    'mode', 'model', 'mosek', 'nodesep', 'nojustify', 'normalize', 'nslimit',
    'nslimit1', 'ordering', 'orientation', 'outputorder', 'overlap',
    'overlap_scaling', 'pack', 'packmode', 'pad', 'page', 'pagedir',
    'quadtree', 'quantum', 'rankdir', 'ranksep', 'ratio', 'remincross',
    'repulsiveforce', 'resolution', 'root', 'rotate', 'searchsize', 'sep',
    'showboxes', 'size', 'smoothing', 'sortv', 'splines', 'start',
    'stylesheet', 'target', 'truecolor', 'viewport', 'voro_margin',
    # for subgraphs
    'rank'
   ])


EDGE_ATTRIBUTES = set([
    'URL', 'arrowhead', 'arrowsize', 'arrowtail',
    'color', 'colorscheme', 'comment', 'constraint', 'decorate', 'dir',
    'edgeURL', 'edgehref', 'edgetarget', 'edgetooltip', 'fontcolor',
    'fontname', 'fontsize', 'headURL', 'headclip', 'headhref', 'headlabel',
    'headport', 'headtarget', 'headtooltip', 'href', 'id', 'label',
    'labelURL', 'labelangle', 'labeldistance', 'labelfloat', 'labelfontcolor',
    'labelfontname', 'labelfontsize', 'labelhref', 'labeltarget',
    'labeltooltip', 'layer', 'len', 'lhead', 'lp', 'ltail', 'minlen',
    'nojustify', 'penwidth', 'pos', 'samehead', 'sametail', 'showboxes',
    'style', 'tailURL', 'tailclip', 'tailhref', 'taillabel', 'tailport',
    'tailtarget', 'tailtooltip', 'target', 'tooltip', 'weight',
    'rank'
   ])


NODE_ATTRIBUTES = set([
    'URL', 'color', 'colorscheme', 'comment',
    'distortion', 'fillcolor', 'fixedsize', 'fontcolor', 'fontname',
    'fontsize', 'group', 'height', 'id', 'image', 'imagescale', 'label',
    'labelloc', 'layer', 'margin', 'nojustify', 'orientation', 'penwidth',
    'peripheries', 'pin', 'pos', 'rects', 'regular', 'root', 'samplepoints',
    'shape', 'shapefile', 'showboxes', 'sides', 'skew', 'sortv', 'style',
    'target', 'tooltip', 'vertices', 'width', 'z',
    # The following are attributes dot2tex
    'texlbl', 'texmode'
   ])


CLUSTER_ATTRIBUTES = set([
    'K', 'URL', 'bgcolor', 'color', 'colorscheme',
    'fillcolor', 'fontcolor', 'fontname', 'fontsize', 'label', 'labeljust',
    'labelloc', 'lheight', 'lp', 'lwidth', 'nojustify', 'pencolor',
    'penwidth', 'peripheries', 'sortv', 'style', 'target', 'tooltip'
   ])


def is_string_like(obj): # from John Hunter, types-free version
    """Check if obj is string."""
    try:
        obj + ''
    except (TypeError, ValueError):
        return False
    return True

def get_fobj(fname, mode='w+'):
    """Obtain a proper file object.

    Parameters
    ----------
    fname : string, file object, file descriptor
        If a string or file descriptor, then we create a file object. If *fname*
        is a file object, then we do nothing and ignore the specified *mode*
        parameter.
    mode : str
        The mode of the file to be opened.

    Returns
    -------
    fobj : file object
        The file object.
    close : bool
        If *fname* was a string, then *close* will be *True* to signify that
        the file object should be closed after writing to it. Otherwise, *close*
        will be *False* signifying that the user, in essence, created the file
        object already and that subsequent operations should not close it.

    """
    if is_string_like(fname):
        fobj = open(fname, mode)
        close = True
    elif hasattr(fname, 'write'):
        # fname is a file-like object, perhaps a StringIO (for example)
        fobj = fname
        close = False
    else:
        # assume it is a file descriptor
        fobj = os.fdopen(fname, mode)
        close = False
    return fobj, close


#
# Extented version of ASPN's Python Cookbook Recipe:
# Frozen dictionaries.
# http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/414283
#
# This version freezes dictionaries used as values within dictionaries.
#
class frozendict(dict):
    def _blocked_attribute(obj):
        raise AttributeError("A frozendict cannot be modified.")
    _blocked_attribute = property(_blocked_attribute)

    __delitem__ = __setitem__ = clear = _blocked_attribute
    pop = popitem = setdefault = update = _blocked_attribute

    def __new__(cls, *args, **kw):
        new = dict.__new__(cls)

        args_ = []
        for arg in args:
            if isinstance(arg, dict):
                arg = copy.copy(arg)
                for k, v in arg.items():
                    if isinstance(v, frozendict):
                        arg[k] = v
                    elif isinstance(v, dict):
                        arg[k] = frozendict(v)
                    elif isinstance(v, list):
                        v_ = list()
                        for elm in v:
                            if isinstance(elm, dict):
                                v_.append(frozendict(elm))
                            else:
                                v_.append(elm)
                        arg[k] = tuple(v_)
                args_.append(arg)
            else:
                args_.append(arg)

        dict.__init__(new, *args_, **kw)
        return new

    def __init__(self, *args, **kw):
        pass

    def __hash__(self):
        try:
            return self._cached_hash
        except AttributeError:
            h = self._cached_hash = hash(tuple(sorted(self.items())))
            return h

    def __repr__(self):
        return "frozendict(%s)" % dict.__repr__(self)


dot_keywords = ['graph', 'subgraph', 'digraph', 'node', 'edge', 'strict']

id_re_alpha_nums = re.compile('^[_a-zA-Z][a-zA-Z0-9_,]*$', re.UNICODE)
id_re_alpha_nums_with_ports = re.compile(
    '^[_a-zA-Z][a-zA-Z0-9_,:\"]*[a-zA-Z0-9_,\"]+$', re.UNICODE
    )
id_re_num = re.compile('^[0-9,]+$', re.UNICODE)
id_re_with_port = re.compile('^([^:]*):([^:]*)$', re.UNICODE)
id_re_dbl_quoted = re.compile('^\".*\"$', re.S | re.UNICODE)
id_re_html = re.compile('^<.*>$', re.S | re.UNICODE)


def needs_quotes(s):
    """Checks whether a string is a dot language ID.

    It will check whether the string is solely composed
    by the characters allowed in an ID or not.
    If the string is one of the reserved keywords it will
    need quotes too but the user will need to add them
    manually.
    """

    # If the name is a reserved keyword it will need quotes but pydot
    # can't tell when it's being used as a keyword or when it's simply
    # a name. Hence the user needs to supply the quotes when an element
    # would use a reserved keyword as name. This function will return
    # false indicating that a keyword string, if provided as-is, won't
    # need quotes.
    if s in dot_keywords:
        return False

    chars = [ord(c) for c in s if ord(c) > 0x7f or ord(c) == 0]
    if chars and not id_re_dbl_quoted.match(s) and not id_re_html.match(s):
        return True

    for test_re in [
            id_re_alpha_nums, id_re_num, id_re_dbl_quoted,
            id_re_html, id_re_alpha_nums_with_ports
           ]:
        if test_re.match(s):
            return False

    m = id_re_with_port.match(s)
    if m:
        return needs_quotes(m.group(1)) or needs_quotes(m.group(2))

    return True


def quote_if_necessary(s):
    # Older versions of graphviz throws a syntax error for empty values without
    # quotes, e.g. [label=]
    if s == '':
        return '""'

    if isinstance(s, bool):
        if s is True:
            return 'True'
        return 'False'

    if not isinstance(s, basestring):
        return s

    if not s:
        return s

    if needs_quotes(s):
        replace = {'"': r'\"', "\n": r'\n', "\r": r'\r'}
        for (a, b) in replace.items():
            s = s.replace(a, b)

        return '"' + s + '"'

    return s


def graph_from_dot_data(data):
    """Load graph as defined by data in DOT format.

    The data is assumed to be in DOT format. It will
    be parsed and a Dot class will be returned,
    representing the graph.
    """

    return dot_parser.parse_dot_data(data)


def graph_from_dot_file(path):
    """Load graph as defined by a DOT file.

    The file is assumed to be in DOT format. It will
    be loaded, parsed and a Dot class will be returned,
    representing the graph.
    """

    fd = open(path, 'rb')
    data = fd.read()
    fd.close()

    return graph_from_dot_data(data)


def graph_from_edges(edge_list, node_prefix='', directed=False):
    """Creates a basic graph out of an edge list.

    The edge list has to be a list of tuples representing
    the nodes connected by the edge.
    The values can be anything: bool, int, float, str.

    If the graph is undirected by default, it is only
    calculated from one of the symmetric halves of the matrix.
    """

    if directed:
        graph = Dot(graph_type='digraph')

    else:
        graph = Dot(graph_type='graph')

    for edge in edge_list:

        if isinstance(edge[0], str):
            src = node_prefix + edge[0]
        else:
            src = node_prefix + str(edge[0])

        if isinstance(edge[1], str):
            dst = node_prefix + edge[1]
        else:
            dst = node_prefix + str(edge[1])

        e = Edge(src, dst)
        graph.add_edge(e)

    return graph


def graph_from_adjacency_matrix(matrix, node_prefix='', directed=False):
    """Creates a basic graph out of an adjacency matrix.

    The matrix has to be a list of rows of values
    representing an adjacency matrix.
    The values can be anything: bool, int, float, as long
    as they can evaluate to True or False.
    """

    node_orig = 1

    if directed:
        graph = Dot(graph_type='digraph')
    else:
        graph = Dot(graph_type='graph')

    for row in matrix:
        if not directed:
            skip = matrix.index(row)
            r = row[skip:]
        else:
            skip = 0
            r = row
        node_dest = skip + 1

        for e in r:
            if e:
                graph.add_edge(
                    Edge(
                        node_prefix + node_orig,
                        node_prefix + node_dest
                        )
                    )
            node_dest += 1
        node_orig += 1

    return graph


def graph_from_incidence_matrix(matrix, node_prefix='', directed=False):
    """Creates a basic graph out of an incidence matrix.

    The matrix has to be a list of rows of values
    representing an incidence matrix.
    The values can be anything: bool, int, float, as long
    as they can evaluate to True or False.
    """

    if directed:
        graph = Dot(graph_type='digraph')
    else:
        graph = Dot(graph_type='graph')

    for row in matrix:
        nodes = []
        c = 1

        for node in row:
            if node:
                nodes.append(c * node)
            c += 1

        nodes.sort()

        if len(nodes) == 2:
            graph.add_edge(
                Edge(
                    node_prefix + abs(nodes[0]),
                    node_prefix + nodes[1]
                    )
                )

    if not directed:
        graph.set_simplify(True)

    return graph


def __find_executables(path):
    """Used by find_graphviz

    path - single directory as a string

    If any of the executables are found, it will return a dictionary
    containing the program names as keys and their paths as values.

    Otherwise returns None
    """

    success = False
    progs = {'dot': '', 'twopi': '', 'neato': '', 'circo': '', 'fdp': '', 'sfdp': ''}

    was_quoted = False
    path = path.strip()
    if path.startswith('"') and path.endswith('"'):
        path = path[1:-1]
        was_quoted = True

    if os.path.isdir(path):
        for prg in progs.keys():
            if progs[prg]:
                continue

            if os.path.exists(os.path.join(path, prg)):
                if was_quoted:
                    progs[prg] = '"' + os.path.join(path, prg) + '"'
                else:
                    progs[prg] = os.path.join(path, prg)

                success = True

            elif os.path.exists(os.path.join(path, prg + '.exe')):
                if was_quoted:
                    progs[prg] = '"' + os.path.join(path, prg + '.exe') + '"'
                else:
                    progs[prg] = os.path.join(path, prg + '.exe')

                success = True

    if success:
        return progs
    else:
        return None


# The multi-platform version of this 'find_graphviz' function was
# contributed by Peter Cock
def find_graphviz():
    """Locate Graphviz's executables in the system.

    Tries three methods:

    First: Windows Registry (Windows only)
    This requires Mark Hammond's pywin32 is installed.

    Secondly: Search the path
    It will look for 'dot', 'twopi' and 'neato' in all the directories
    specified in the PATH environment variable.

    Thirdly: Default install location (Windows only)
    It will look for 'dot', 'twopi' and 'neato' in the default install
    location under the "Program Files" directory.

    It will return a dictionary containing the program names as keys
    and their paths as values.

    If this fails, it returns None.
    """

    # Method 1 (Windows only)
    if os.sys.platform == 'win32':

        HKEY_LOCAL_MACHINE = 0x80000002
        KEY_QUERY_VALUE = 0x0001

        RegOpenKeyEx = None
        RegQueryValueEx = None
        RegCloseKey = None

        try:
            import win32api
            RegOpenKeyEx = win32api.RegOpenKeyEx
            RegQueryValueEx = win32api.RegQueryValueEx
            RegCloseKey = win32api.RegCloseKey

        except ImportError:
            # Print a messaged suggesting they install these?
            pass

        try:
            import ctypes

            def RegOpenKeyEx(key, subkey, opt, sam):
                result = ctypes.c_uint(0)
                ctypes.windll.advapi32.RegOpenKeyExA(key, subkey, opt, sam, ctypes.byref(result))
                return result.value

            def RegQueryValueEx(hkey, valuename):
                data_type = ctypes.c_uint(0)
                data_len = ctypes.c_uint(1024)
                data = ctypes.create_string_buffer(1024)

                # this has a return value, which we should probably check
                ctypes.windll.advapi32.RegQueryValueExA(
                    hkey, valuename, 0, ctypes.byref(data_type),
                    data, ctypes.byref(data_len)
                    )

                return data.value

            RegCloseKey = ctypes.windll.advapi32.RegCloseKey

        except ImportError:
            # Print a messaged suggesting they install these?
            pass

        if RegOpenKeyEx is not None:
            # Get the GraphViz install path from the registry
            hkey = None
            potentialKeys = [
                "SOFTWARE\\ATT\\Graphviz",
                "SOFTWARE\\AT&T Research Labs\\Graphviz"
                ]
            for potentialKey in potentialKeys:

                try:
                    hkey = RegOpenKeyEx(
                        HKEY_LOCAL_MACHINE,
                        potentialKey, 0, KEY_QUERY_VALUE
                        )

                    if hkey is not None:
                        path = RegQueryValueEx(hkey, "InstallPath")
                        RegCloseKey(hkey)

                        # The regitry variable might exist, left by old installations
                        # but with no value, in those cases we keep searching...
                        if not path:
                            continue

                        # Now append the "bin" subdirectory:
                        path = os.path.join(path, "bin")
                        progs = __find_executables(path)
                        if progs is not None:
                            #print("Used Windows registry")
                            return progs

                except Exception:
                    #raise
                    pass
                else:
                    break

    # Method 2 (Linux, Windows etc)
    if 'PATH' in os.environ:
        for path in os.environ['PATH'].split(os.pathsep):
            progs = __find_executables(path)
            if progs is not None:
                #print("Used path")
                return progs

    # Method 3 (Windows only)
    if os.sys.platform == 'win32':

        # Try and work out the equivalent of "C:\Program Files" on this
        # machine (might be on drive D:, or in a different language)
        if 'PROGRAMFILES' in os.environ:
            # Note, we could also use the win32api to get this
            # information, but win32api may not be installed.
            path = os.path.join(os.environ['PROGRAMFILES'], 'ATT', 'GraphViz', 'bin')
        else:
            #Just in case, try the default...
            path = r"C:\Program Files\att\Graphviz\bin"

        progs = __find_executables(path)

        if progs is not None:

            #print("Used default install location")
            return progs

    for path in (
            '/usr/bin', '/usr/local/bin',
            '/opt/local/bin',
            '/opt/bin', '/sw/bin', '/usr/share',
            '/Applications/Graphviz.app/Contents/MacOS/'
            ):

        progs = __find_executables(path)
        if progs is not None:
            #print("Used path")
            return progs

    # Failed to find GraphViz
    return None


class Common(object):
    """Common information to several classes.

    Should not be directly used, several classes are derived from
    this one.
    """

    def __getstate__(self):

        dict = copy.copy(self.obj_dict)

        return dict

    def __setstate__(self, state):

        self.obj_dict = state

    def __get_attribute__(self, attr):
        """Look for default attributes for this node"""

        attr_val = self.obj_dict['attributes'].get(attr, None)

        if attr_val is None:
            # get the defaults for nodes/edges

            default_node_name = self.obj_dict['type']

            # The defaults for graphs are set on a node named 'graph'
            if default_node_name in ('subgraph', 'digraph', 'cluster'):
                default_node_name = 'graph'

            g = self.get_parent_graph()
            if g is not None:
                defaults = g.get_node(default_node_name)
            else:
                return None

            # Multiple defaults could be set by having repeated 'graph [...]'
            # 'node [...]', 'edge [...]' statements. In such case, if the
            # same attribute is set in different statements, only the first
            # will be returned. In order to get all, one would call the
            # get_*_defaults() methods and handle those. Or go node by node
            # (of the ones specifying defaults) and modify the attributes
            # individually.
            #
            if not isinstance(defaults, (list, tuple)):
                defaults = [defaults]

            for default in defaults:
                attr_val = default.obj_dict['attributes'].get(attr, None)
                if attr_val:
                    return attr_val
        else:
            return attr_val

        return None

    def set_parent_graph(self, parent_graph):

        self.obj_dict['parent_graph'] = parent_graph

    def get_parent_graph(self):

        return self.obj_dict.get('parent_graph', None)

    def set(self, name, value):
        """Set an attribute value by name.

        Given an attribute 'name' it will set its value to 'value'.
        There's always the possibility of using the methods:

            set_'name'(value)

        which are defined for all the existing attributes.
        """

        self.obj_dict['attributes'][name] = value

    def get(self, name):
        """Get an attribute value by name.

        Given an attribute 'name' it will get its value.
        There's always the possibility of using the methods:

            get_'name'()

        which are defined for all the existing attributes.
        """

        return self.obj_dict['attributes'].get(name, None)

    def get_attributes(self):
        """"""

        return self.obj_dict['attributes']

    def set_sequence(self, seq):

        self.obj_dict['sequence'] = seq

    def get_sequence(self):

        return self.obj_dict['sequence']

    def create_attribute_methods(self, obj_attributes):

        #for attr in self.obj_dict['attributes']:
        for attr in obj_attributes:

            # Generate all the Setter methods.
            #
            self.__setattr__(
                'set_' + attr,
                lambda x, a=attr: self.obj_dict['attributes'].__setitem__(a, x)
                )

            # Generate all the Getter methods.
            #
            self.__setattr__('get_' + attr, lambda a=attr: self.__get_attribute__(a))


class Error(Exception):
    """General error handling class.
    """
    def __init__(self, value):
        self.value = value

    def __str__(self):
        return self.value


class InvocationException(Exception):
    """To indicate that a ploblem occurred while running any of the GraphViz executables.
    """
    def __init__(self, value):
        self.value = value

    def __str__(self):
        return self.value


class Node(Common):
    """A graph node.

    This class represents a graph's node with all its attributes.

    node(name, attribute=value, ...)

    name: node's name

    All the attributes defined in the Graphviz dot language should
    be supported.
    """

    def __init__(self, name='', obj_dict=None, **attrs):

        #
        # Nodes will take attributes of all other types because the defaults
        # for any GraphViz object are dealt with as if they were Node definitions
        #

        if obj_dict is not None:
            self.obj_dict = obj_dict
        else:
            self.obj_dict = dict()

            # Copy the attributes
            #
            self.obj_dict['attributes'] = dict(attrs)
            self.obj_dict['type'] = 'node'
            self.obj_dict['parent_graph'] = None
            self.obj_dict['parent_node_list'] = None
            self.obj_dict['sequence'] = None

            # Remove the compass point
            #
            port = None
            if isinstance(name, basestring) and not name.startswith('"'):
                idx = name.find(':')
                if idx > 0 and idx + 1 < len(name):
                    name, port = name[:idx], name[idx:]

            if isinstance(name, (long, int)):
                name = str(name)

            self.obj_dict['name'] = quote_if_necessary(name)
            self.obj_dict['port'] = port

        self.create_attribute_methods(NODE_ATTRIBUTES)

    def set_name(self, node_name):
        """Set the node's name."""

        self.obj_dict['name'] = node_name

    def get_name(self):
        """Get the node's name."""

        return self.obj_dict['name']

    def get_port(self):
        """Get the node's port."""

        return self.obj_dict['port']

    def add_style(self, style):

        styles = self.obj_dict['attributes'].get('style', None)
        if not styles and style:
            styles = [style]
        else:
            styles = styles.split(',')
            styles.append(style)

        self.obj_dict['attributes']['style'] = ','.join(styles)

    def to_string(self):
        """Returns a string representation of the node in dot language.
        """

        # RMF: special case defaults for node, edge and graph properties.
        #
        node = quote_if_necessary(self.obj_dict['name'])

        node_attr = list()

        for attr, value in sorted(self.obj_dict['attributes'].items(), key=itemgetter(0)):
            if value is not None:
                node_attr.append('%s=%s' % (attr, quote_if_necessary(value)))
            else:
                node_attr.append(attr)

        # No point in having nodes setting any defaults if the don't set
        # any attributes...
        #
        if node in ('graph', 'node', 'edge') and len(node_attr) == 0:
            return ''

        node_attr = ', '.join(node_attr)

        if node_attr:
            node += ' [' + node_attr + ']'

        return node + ';'


class Edge(Common):
    """A graph edge.

    This class represents a graph's edge with all its attributes.

    edge(src, dst, attribute=value, ...)

    src: source node's name
    dst: destination node's name

    All the attributes defined in the Graphviz dot language should
    be supported.

    Attributes can be set through the dynamically generated methods:

     set_[attribute name], i.e. set_label, set_fontname

    or directly by using the instance's special dictionary:

     Edge.obj_dict['attributes'][attribute name], i.e.

        edge_instance.obj_dict['attributes']['label']
        edge_instance.obj_dict['attributes']['fontname']

    """

    def __init__(self, src='', dst='', obj_dict=None, **attrs):

        if isinstance(src, (list, tuple)) and dst == '':
            src, dst = src

        if obj_dict is not None:

            self.obj_dict = obj_dict

        else:

            self.obj_dict = dict()

            # Copy the attributes
            #
            self.obj_dict['attributes'] = dict(attrs)
            self.obj_dict['type'] = 'edge'
            self.obj_dict['parent_graph'] = None
            self.obj_dict['parent_edge_list'] = None
            self.obj_dict['sequence'] = None

            if isinstance(src, Node):
                src = src.get_name()

            if isinstance(dst, Node):
                dst = dst.get_name()

            points = (quote_if_necessary(src), quote_if_necessary(dst))

            self.obj_dict['points'] = points

        self.create_attribute_methods(EDGE_ATTRIBUTES)

    def get_source(self):
        """Get the edges source node name."""

        return self.obj_dict['points'][0]

    def get_destination(self):
        """Get the edge's destination node name."""

        return self.obj_dict['points'][1]

    def __hash__(self):
        return hash(hash(self.get_source()) + hash(self.get_destination()))

    def __eq__(self, edge):
        """Compare two edges.

        If the parent graph is directed, arcs linking
        node A to B are considered equal and A->B != B->A

        If the parent graph is undirected, any edge
        connecting two nodes is equal to any other
        edge connecting the same nodes, A->B == B->A
        """

        if not isinstance(edge, Edge):
            raise Error("Can't compare and edge to a non-edge object.")

        if self.get_parent_graph().get_top_graph_type() == 'graph':

            # If the graph is undirected, the edge has neither
            # source nor destination.
            #
            if ((self.get_source() == edge.get_source() and
                    self.get_destination() == edge.get_destination()) or
                (edge.get_source() == self.get_destination() and
                    edge.get_destination() == self.get_source())):
                return True

        else:
            if (self.get_source() == edge.get_source() and
                    self.get_destination() == edge.get_destination()):
                return True

        return False

    def parse_node_ref(self, node_str):

        if not isinstance(node_str, str):
            return node_str

        if node_str.startswith('"') and node_str.endswith('"'):
            return node_str

        node_port_idx = node_str.rfind(':')

        if (node_port_idx > 0 and node_str[0] == '"' and
                node_str[node_port_idx - 1] == '"'):
            return node_str

        if node_port_idx > 0:
            a = node_str[:node_port_idx]
            b = node_str[node_port_idx + 1:]

            node = quote_if_necessary(a)

            node += ':' + quote_if_necessary(b)

            return node

        return node_str

    def to_string(self):
        """Returns a string representation of the edge in dot language.
        """

        src = self.parse_node_ref(self.get_source())
        dst = self.parse_node_ref(self.get_destination())

        if isinstance(src, frozendict):
            edge = [Subgraph(obj_dict=src).to_string()]
        elif isinstance(src, (int, long)):
            edge = [str(src)]
        else:
            edge = [src]

        if (self.get_parent_graph() and
                self.get_parent_graph().get_top_graph_type() and
                self.get_parent_graph().get_top_graph_type() == 'digraph'):

            edge.append('->')

        else:
            edge.append('--')

        if isinstance(dst, frozendict):
            edge.append(Subgraph(obj_dict=dst).to_string())
        elif isinstance(dst, (int, long)):
            edge.append(str(dst))
        else:
            edge.append(dst)

        edge_attr = list()

        for attr, value in sorted(self.obj_dict['attributes'].items(), key=itemgetter(0)):
            if value is not None:
                edge_attr.append('%s=%s' % (attr, quote_if_necessary(value)))
            else:
                edge_attr.append(attr)

        edge_attr = ', '.join(edge_attr)

        if edge_attr:
            edge.append(' [' + edge_attr + ']')

        return ' '.join(edge) + ';'


class Graph(Common):
    """Class representing a graph in Graphviz's dot language.

    This class implements the methods to work on a representation
    of a graph in Graphviz's dot language.

    graph(graph_name='G', graph_type='digraph',
        strict=False, suppress_disconnected=False, attribute=value, ...)

    graph_name:
        the graph's name
    graph_type:
        can be 'graph' or 'digraph'
    suppress_disconnected:
        defaults to False, which will remove from the
        graph any disconnected nodes.
    simplify:
        if True it will avoid displaying equal edges, i.e.
        only one edge between two nodes. removing the
        duplicated ones.

    All the attributes defined in the Graphviz dot language should
    be supported.

    Attributes can be set through the dynamically generated methods:

     set_[attribute name], i.e. set_size, set_fontname

    or using the instance's attributes:

     Graph.obj_dict['attributes'][attribute name], i.e.

        graph_instance.obj_dict['attributes']['label']
        graph_instance.obj_dict['attributes']['fontname']
    """

    def __init__(
            self, graph_name='G', obj_dict=None, graph_type='digraph', strict=False,
            suppress_disconnected=False, simplify=False, **attrs):

        if obj_dict is not None:
            self.obj_dict = obj_dict
        else:
            self.obj_dict = dict()

            self.obj_dict['attributes'] = dict(attrs)

            if graph_type not in ['graph', 'digraph']:
                raise Error((
                    'Invalid type "%s". Accepted graph types are: '
                    'graph, digraph, subgraph' % graph_type
                    ))

            self.obj_dict['name'] = quote_if_necessary(graph_name)
            self.obj_dict['type'] = graph_type

            self.obj_dict['strict'] = strict
            self.obj_dict['suppress_disconnected'] = suppress_disconnected
            self.obj_dict['simplify'] = simplify

            self.obj_dict['current_child_sequence'] = 1
            self.obj_dict['nodes'] = dict()
            self.obj_dict['edges'] = dict()
            self.obj_dict['subgraphs'] = dict()

            self.set_parent_graph(self)

        self.create_attribute_methods(GRAPH_ATTRIBUTES)

    def get_graph_type(self):
        return self.obj_dict['type']

    def get_top_graph_type(self):
        parent = self
        while True:
            parent_ = parent.get_parent_graph()
            if parent_ == parent:
                break
            parent = parent_

        return parent.obj_dict['type']

    def set_graph_defaults(self, **attrs):
        self.add_node(Node('graph', **attrs))

    def get_graph_defaults(self, **attrs):

        graph_nodes = self.get_node('graph')

        if isinstance(graph_nodes, (list, tuple)):
            return [node.get_attributes() for node in graph_nodes]

        return graph_nodes.get_attributes()

    def set_node_defaults(self, **attrs):
        self.add_node(Node('node', **attrs))

    def get_node_defaults(self, **attrs):
        graph_nodes = self.get_node('node')

        if isinstance(graph_nodes, (list, tuple)):
            return [node.get_attributes() for node in graph_nodes]

        return graph_nodes.get_attributes()

    def set_edge_defaults(self, **attrs):
        self.add_node(Node('edge', **attrs))

    def get_edge_defaults(self, **attrs):
        graph_nodes = self.get_node('edge')

        if isinstance(graph_nodes, (list, tuple)):
            return [node.get_attributes() for node in graph_nodes]

        return graph_nodes.get_attributes()

    def set_simplify(self, simplify):
        """Set whether to simplify or not.

        If True it will avoid displaying equal edges, i.e.
        only one edge between two nodes. removing the
        duplicated ones.
        """

        self.obj_dict['simplify'] = simplify

    def get_simplify(self):
        """Get whether to simplify or not.

        Refer to set_simplify for more information.
        """

        return self.obj_dict['simplify']

    def set_type(self, graph_type):
        """Set the graph's type, 'graph' or 'digraph'."""

        self.obj_dict['type'] = graph_type

    def get_type(self):
        """Get the graph's type, 'graph' or 'digraph'."""

        return self.obj_dict['type']

    def set_name(self, graph_name):
        """Set the graph's name."""

        self.obj_dict['name'] = graph_name

    def get_name(self):
        """Get the graph's name."""

        return self.obj_dict['name']

    def set_strict(self, val):
        """Set graph to 'strict' mode.

        This option is only valid for top level graphs.
        """

        self.obj_dict['strict'] = val

    def get_strict(self, val):
        """Get graph's 'strict' mode (True, False).

        This option is only valid for top level graphs.
        """

        return self.obj_dict['strict']

    def set_suppress_disconnected(self, val):
        """Suppress disconnected nodes in the output graph.

        This option will skip nodes in the graph with no incoming or outgoing
        edges. This option works also for subgraphs and has effect only in the
        current graph/subgraph.
        """

        self.obj_dict['suppress_disconnected'] = val

    def get_suppress_disconnected(self, val):
        """Get if suppress disconnected is set.

        Refer to set_suppress_disconnected for more information.
        """

        return self.obj_dict['suppress_disconnected']

    def get_next_sequence_number(self):
        seq = self.obj_dict['current_child_sequence']
        self.obj_dict['current_child_sequence'] += 1
        return seq

    def add_node(self, graph_node):
        """Adds a node object to the graph.

        It takes a node object as its only argument and returns
        None.
        """

        if not isinstance(graph_node, Node):
            raise TypeError('add_node() received a non node class object: ' + str(graph_node))

        node = self.get_node(graph_node.get_name())

        if not node:
            self.obj_dict['nodes'][graph_node.get_name()] = [graph_node.obj_dict]

            #self.node_dict[graph_node.get_name()] = graph_node.attributes
            graph_node.set_parent_graph(self.get_parent_graph())
        else:
            self.obj_dict['nodes'][graph_node.get_name()].append(graph_node.obj_dict)

        graph_node.set_sequence(self.get_next_sequence_number())

    def del_node(self, name, index=None):
        """Delete a node from the graph.

        Given a node's name all node(s) with that same name
        will be deleted if 'index' is not specified or set
        to None.
        If there are several nodes with that same name and
        'index' is given, only the node in that position
        will be deleted.

        'index' should be an integer specifying the position
        of the node to delete. If index is larger than the
        number of nodes with that name, no action is taken.

        If nodes are deleted it returns True. If no action
        is taken it returns False.
        """

        if isinstance(name, Node):
            name = name.get_name()

        if name in self.obj_dict['nodes']:
            if index is not None and index < len(self.obj_dict['nodes'][name]):
                del self.obj_dict['nodes'][name][index]
                return True
            else:
                del self.obj_dict['nodes'][name]
                return True

        return False

    def get_node(self, name):
        """Retrieve a node from the graph.

        Given a node's name the corresponding Node
        instance will be returned.

        If one or more nodes exist with that name a list of
        Node instances is returned.
        An empty list is returned otherwise.
        """

        match = list()

        if name in self.obj_dict['nodes']:
            match.extend([
                Node(obj_dict=obj_dict)
                for obj_dict
                in self.obj_dict['nodes'][name]
                ])

        return match

    def get_nodes(self):
        """Get the list of Node instances."""

        return self.get_node_list()

    def get_node_list(self):
        """Get the list of Node instances.

        This method returns the list of Node instances
        composing the graph.
        """

        node_objs = list()

        for node, obj_dict_list in self.obj_dict['nodes'].items():
            node_objs.extend([
                Node(obj_dict=obj_d)
                for obj_d
                in obj_dict_list
                ])

        return node_objs

    def add_edge(self, graph_edge):
        """Adds an edge object to the graph.

        It takes a edge object as its only argument and returns
        None.
        """

        if not isinstance(graph_edge, Edge):
            raise TypeError('add_edge() received a non edge class object: ' + str(graph_edge))

        edge_points = (graph_edge.get_source(), graph_edge.get_destination())

        if edge_points in self.obj_dict['edges']:

            edge_list = self.obj_dict['edges'][edge_points]
            edge_list.append(graph_edge.obj_dict)
        else:
            self.obj_dict['edges'][edge_points] = [graph_edge.obj_dict]

        graph_edge.set_sequence(self.get_next_sequence_number())
        graph_edge.set_parent_graph(self.get_parent_graph())

    def del_edge(self, src_or_list, dst=None, index=None):
        """Delete an edge from the graph.

        Given an edge's (source, destination) node names all
        matching edges(s) will be deleted if 'index' is not
        specified or set to None.
        If there are several matching edges and 'index' is
        given, only the edge in that position will be deleted.

        'index' should be an integer specifying the position
        of the edge to delete. If index is larger than the
        number of matching edges, no action is taken.

        If edges are deleted it returns True. If no action
        is taken it returns False.
        """

        if isinstance(src_or_list, (list, tuple)):
            if dst is not None and isinstance(dst, (int, long)):
                index = dst
            src, dst = src_or_list
        else:
            src, dst = src_or_list, dst

        if isinstance(src, Node):
            src = src.get_name()

        if isinstance(dst, Node):
            dst = dst.get_name()

        if (src, dst) in self.obj_dict['edges']:
            if index is not None and index < len(self.obj_dict['edges'][(src, dst)]):
                del self.obj_dict['edges'][(src, dst)][index]
                return True
            else:
                del self.obj_dict['edges'][(src, dst)]
                return True

        return False

    def get_edge(self, src_or_list, dst=None):
        """Retrieved an edge from the graph.

        Given an edge's source and destination the corresponding
        Edge instance(s) will be returned.

        If one or more edges exist with that source and destination
        a list of Edge instances is returned.
        An empty list is returned otherwise.
        """

        if isinstance(src_or_list, (list, tuple)) and dst is None:
            edge_points = tuple(src_or_list)
            edge_points_reverse = (edge_points[1], edge_points[0])
        else:
            edge_points = (src_or_list, dst)
            edge_points_reverse = (dst, src_or_list)

        match = list()

        if edge_points in self.obj_dict['edges'] or (
                self.get_top_graph_type() == 'graph' and
                edge_points_reverse in self.obj_dict['edges']
                ):

            edges_obj_dict = self.obj_dict['edges'].get(
                edge_points,
                self.obj_dict['edges'].get(edge_points_reverse, None))

            for edge_obj_dict in edges_obj_dict:
                match.append(
                    Edge(edge_points[0], edge_points[1], obj_dict=edge_obj_dict)
                    )

        return match

    def get_edges(self):
        return self.get_edge_list()

    def get_edge_list(self):
        """Get the list of Edge instances.

        This method returns the list of Edge instances
        composing the graph.
        """

        edge_objs = list()

        for edge, obj_dict_list in self.obj_dict['edges'].items():
            edge_objs.extend([
                Edge(obj_dict=obj_d)
                for obj_d
                in obj_dict_list
                ])

        return edge_objs

    def add_subgraph(self, sgraph):
        """Adds an subgraph object to the graph.

        It takes a subgraph object as its only argument and returns
        None.
        """

        if not isinstance(sgraph, Subgraph) and not isinstance(sgraph, Cluster):
            raise TypeError('add_subgraph() received a non subgraph class object:' + str(sgraph))

        if sgraph.get_name() in self.obj_dict['subgraphs']:

            sgraph_list = self.obj_dict['subgraphs'][sgraph.get_name()]
            sgraph_list.append(sgraph.obj_dict)

        else:
            self.obj_dict['subgraphs'][sgraph.get_name()] = [sgraph.obj_dict]

        sgraph.set_sequence(self.get_next_sequence_number())

        sgraph.set_parent_graph(self.get_parent_graph())

    def get_subgraph(self, name):
        """Retrieved a subgraph from the graph.

        Given a subgraph's name the corresponding
        Subgraph instance will be returned.

        If one or more subgraphs exist with the same name, a list of
        Subgraph instances is returned.
        An empty list is returned otherwise.
        """

        match = list()

        if name in self.obj_dict['subgraphs']:
            sgraphs_obj_dict = self.obj_dict['subgraphs'].get(name)

            for obj_dict_list in sgraphs_obj_dict:
                #match.extend(Subgraph(obj_dict = obj_d) for obj_d in obj_dict_list)
                match.append(Subgraph(obj_dict=obj_dict_list))

        return match

    def get_subgraphs(self):
        return self.get_subgraph_list()

    def get_subgraph_list(self):
        """Get the list of Subgraph instances.

        This method returns the list of Subgraph instances
        in the graph.
        """

        sgraph_objs = list()

        for sgraph, obj_dict_list in self.obj_dict['subgraphs'].items():
            sgraph_objs.extend([
                Subgraph(obj_dict=obj_d)
                for obj_d
                in obj_dict_list
                ])

        return sgraph_objs

    def set_parent_graph(self, parent_graph):

        self.obj_dict['parent_graph'] = parent_graph

        for obj_list in self.obj_dict['nodes'].values():
            for obj in obj_list:
                obj['parent_graph'] = parent_graph

        for obj_list in self.obj_dict['edges'].values():
            for obj in obj_list:
                obj['parent_graph'] = parent_graph

        for obj_list in self.obj_dict['subgraphs'].values():
            for obj in obj_list:
                Graph(obj_dict=obj).set_parent_graph(parent_graph)

    def to_string(self):
        """Returns a string representation of the graph in dot language.

        It will return the graph and all its subelements in string from.
        """

        graph = list()

        if self.obj_dict.get('strict', None) is not None:
            if self == self.get_parent_graph() and self.obj_dict['strict']:
                graph.append('strict ')

        if self.obj_dict['name'] == '':
            if 'show_keyword' in self.obj_dict and self.obj_dict['show_keyword']:
                graph.append('subgraph {\n')
            else:
                graph.append('{\n')
        else:
            graph.append('%s %s {\n' % (self.obj_dict['type'], self.obj_dict['name']))

        for attr, value in sorted(self.obj_dict['attributes'].items(), key=itemgetter(0)):
            if value is not None:
                graph.append('%s=%s' % (attr, quote_if_necessary(value)))
            else:
                graph.append(attr)

            graph.append(';\n')

        edges_done = set()

        edge_obj_dicts = list()
        for e in self.obj_dict['edges'].values():
            edge_obj_dicts.extend(e)

        if edge_obj_dicts:
            edge_src_set, edge_dst_set = list(zip(*[obj['points'] for obj in edge_obj_dicts]))
            edge_src_set, edge_dst_set = set(edge_src_set), set(edge_dst_set)
        else:
            edge_src_set, edge_dst_set = set(), set()

        node_obj_dicts = list()
        for e in self.obj_dict['nodes'].values():
            node_obj_dicts.extend(e)

        sgraph_obj_dicts = list()
        for sg in self.obj_dict['subgraphs'].values():
            sgraph_obj_dicts.extend(sg)

        obj_list = sorted([
            (obj['sequence'], obj)
            for obj
            in (edge_obj_dicts + node_obj_dicts + sgraph_obj_dicts)
            ])

        for idx, obj in obj_list:
            if obj['type'] == 'node':
                node = Node(obj_dict=obj)

                if self.obj_dict.get('suppress_disconnected', False):
                    if (node.get_name() not in edge_src_set and
                            node.get_name() not in edge_dst_set):
                        continue

                graph.append(node.to_string() + '\n')

            elif obj['type'] == 'edge':
                edge = Edge(obj_dict=obj)

                if self.obj_dict.get('simplify', False) and edge in edges_done:
                    continue

                graph.append(edge.to_string() + '\n')
                edges_done.add(edge)
            else:
                sgraph = Subgraph(obj_dict=obj)
                graph.append(sgraph.to_string() + '\n')

        graph.append('}\n')

        return ''.join(graph)


class Subgraph(Graph):

    """Class representing a subgraph in Graphviz's dot language.

    This class implements the methods to work on a representation
    of a subgraph in Graphviz's dot language.

    subgraph(graph_name='subG', suppress_disconnected=False, attribute=value, ...)

    graph_name:
        the subgraph's name
    suppress_disconnected:
        defaults to false, which will remove from the
        subgraph any disconnected nodes.
    All the attributes defined in the Graphviz dot language should
    be supported.

    Attributes can be set through the dynamically generated methods:

     set_[attribute name], i.e. set_size, set_fontname

    or using the instance's attributes:

     Subgraph.obj_dict['attributes'][attribute name], i.e.

        subgraph_instance.obj_dict['attributes']['label']
        subgraph_instance.obj_dict['attributes']['fontname']
    """

    # RMF: subgraph should have all the attributes of graph so it can be passed
    # as a graph to all methods
    #
    def __init__(
            self, graph_name='', obj_dict=None, suppress_disconnected=False,
            simplify=False, **attrs):

        Graph.__init__(
            self, graph_name=graph_name, obj_dict=obj_dict,
            suppress_disconnected=suppress_disconnected, simplify=simplify, **attrs)

        if obj_dict is None:
            self.obj_dict['type'] = 'subgraph'


class Cluster(Graph):

    """Class representing a cluster in Graphviz's dot language.

    This class implements the methods to work on a representation
    of a cluster in Graphviz's dot language.

    cluster(graph_name='subG', suppress_disconnected=False, attribute=value, ...)

    graph_name:
        the cluster's name (the string 'cluster' will be always prepended)
    suppress_disconnected:
        defaults to false, which will remove from the
        cluster any disconnected nodes.
    All the attributes defined in the Graphviz dot language should
    be supported.

    Attributes can be set through the dynamically generated methods:

     set_[attribute name], i.e. set_color, set_fontname

    or using the instance's attributes:

     Cluster.obj_dict['attributes'][attribute name], i.e.

        cluster_instance.obj_dict['attributes']['label']
        cluster_instance.obj_dict['attributes']['fontname']
    """

    def __init__(
            self, graph_name='subG', obj_dict=None, suppress_disconnected=False,
            simplify=False, **attrs):

        Graph.__init__(
            self, graph_name=graph_name, obj_dict=obj_dict,
            suppress_disconnected=suppress_disconnected, simplify=simplify, **attrs
            )

        if obj_dict is None:
            self.obj_dict['type'] = 'subgraph'
            self.obj_dict['name'] = 'cluster_' + graph_name

        self.create_attribute_methods(CLUSTER_ATTRIBUTES)


class Dot(Graph):
    """A container for handling a dot language file.

    This class implements methods to write and process
    a dot language file. It is a derived class of
    the base class 'Graph'.
    """

    def __init__(self, *argsl, **argsd):
        Graph.__init__(self, *argsl, **argsd)

        self.shape_files = list()
        self.progs = None
        self.formats = [
            'canon', 'cmap', 'cmapx', 'cmapx_np', 'dia', 'dot',
            'fig', 'gd', 'gd2', 'gif', 'hpgl', 'imap', 'imap_np', 'ismap',
            'jpe', 'jpeg', 'jpg', 'mif', 'mp', 'pcl', 'pdf', 'pic', 'plain',
            'plain-ext', 'png', 'ps', 'ps2', 'svg', 'svgz', 'vml', 'vmlz',
            'vrml', 'vtx', 'wbmp', 'xdot', 'xlib'
            ]
        self.prog = 'dot'

        # Automatically creates all the methods enabling the creation
        # of output in any of the supported formats.
        for frmt in self.formats:
            self.__setattr__(
                'create_' + frmt,
                lambda f=frmt, prog=self.prog: self.create(format=f, prog=prog)
                )
            f = self.__dict__['create_' + frmt]
            f.__doc__ = (
                '''Refer to the docstring accompanying the'''
                ''''create' method for more information.'''
                )

        for frmt in self.formats + ['raw']:
            self.__setattr__(
                'write_' + frmt,
                lambda path, f=frmt, prog=self.prog: self.write(path, format=f, prog=prog)
                )

            f = self.__dict__['write_' + frmt]
            f.__doc__ = (
                '''Refer to the docstring accompanying the'''
                ''''write' method for more information.'''
                )

    def __getstate__(self):
        return copy.copy(self.obj_dict)

    def __setstate__(self, state):
        self.obj_dict = state

    def set_shape_files(self, file_paths):
        """Add the paths of the required image files.

        If the graph needs graphic objects to be used as shapes or otherwise
        those need to be in the same folder as the graph is going to be rendered
        from. Alternatively the absolute path to the files can be specified when
        including the graphics in the graph.

        The files in the location pointed to by the path(s) specified as arguments
        to this method will be copied to the same temporary location where the
        graph is going to be rendered.
        """

        if isinstance(file_paths, basestring):
            self.shape_files.append(file_paths)

        if isinstance(file_paths, (list, tuple)):
            self.shape_files.extend(file_paths)

    def set_prog(self, prog):
        """Sets the default program.

        Sets the default program in charge of processing
        the dot file into a graph.
        """
        self.prog = prog

    def set_graphviz_executables(self, paths):
        """This method allows to manually specify the location of the GraphViz executables.

        The argument to this method should be a dictionary where the keys are as follows:

            {'dot': '', 'twopi': '', 'neato': '', 'circo': '', 'fdp': ''}

        and the values are the paths to the corresponding executable, including the name
        of the executable itself.
        """

        self.progs = paths

    def write(self, path, prog=None, format='raw'):
        """
        Given a filename 'path' it will open/create and truncate
        such file and write on it a representation of the graph
        defined by the dot object and in the format specified by
        'format'. 'path' can also be an open file-like object, such as
        a StringIO instance.

        The format 'raw' is used to dump the string representation
        of the Dot object, without further processing.
        The output can be processed by any of graphviz tools, defined
        in 'prog', which defaults to 'dot'
        Returns True or False according to the success of the write
        operation.

        There's also the preferred possibility of using:

            write_'format'(path, prog='program')

        which are automatically defined for all the supported formats.
        [write_ps(), write_gif(), write_dia(), ...]

        """
        if prog is None:
            prog = self.prog

        fobj, close = get_fobj(path, 'w+b')
        try:
            if format == 'raw':
                data = self.to_string()
                if isinstance(data, basestring):
                    if not isinstance(data, unicode):
                        try:
                            data = unicode(data, 'utf-8')
                        except:
                            pass

                try:
                    charset = self.get_charset()
                    if not PY3 or not charset:
                        charset = 'utf-8'
                    data = data.encode(charset)
                except:
                    if PY3:
                        data = data.encode('utf-8')
                    pass

                fobj.write(data)

            else:
                fobj.write(self.create(prog, format))
        finally:
            if close:
                fobj.close()

        return True

    def create(self, prog=None, format='ps'):
        """Creates and returns a Postscript representation of the graph.

        create will write the graph to a temporary dot file and process
        it with the program given by 'prog' (which defaults to 'twopi'),
        reading the Postscript output and returning it as a string is the
        operation is successful.
        On failure None is returned.

        There's also the preferred possibility of using:

            create_'format'(prog='program')

        which are automatically defined for all the supported formats.
        [create_ps(), create_gif(), create_dia(), ...]

        If 'prog' is a list instead of a string the fist item is expected
        to be the program name, followed by any optional command-line
        arguments for it:

            ['twopi', '-Tdot', '-s10']
        """

        if prog is None:
            prog = self.prog

        if isinstance(prog, (list, tuple)):
            prog, args = prog[0], prog[1:]
        else:
            args = []

        if self.progs is None:
            self.progs = find_graphviz()
            if self.progs is None:
                raise InvocationException(
                    'GraphViz\'s executables not found')

        if prog not in self.progs:
            raise InvocationException(
                'GraphViz\'s executable "%s" not found' % prog)

        if not os.path.exists(self.progs[prog]) or not os.path.isfile(self.progs[prog]):
            raise InvocationException(
                'GraphViz\'s executable "%s" is not a file or doesn\'t exist' % self.progs[prog])

        tmp_fd, tmp_name = tempfile.mkstemp()
        os.close(tmp_fd)
        self.write(tmp_name)
        tmp_dir = os.path.dirname(tmp_name)

        # For each of the image files...
        for img in self.shape_files:

            # Get its data
            f = open(img, 'rb')
            f_data = f.read()
            f.close()

            # And copy it under a file with the same name in the temporary directory
            f = open(os.path.join(tmp_dir, os.path.basename(img)), 'wb')
            f.write(f_data)
            f.close()

        cmdline = [self.progs[prog], '-T' + format, tmp_name] + args

        p = subprocess.Popen(
            cmdline,
            cwd=tmp_dir,
            stderr=subprocess.PIPE, stdout=subprocess.PIPE)

        stderr = p.stderr
        stdout = p.stdout

        stdout_output = list()
        while True:
            data = stdout.read()
            if not data:
                break
            stdout_output.append(data)
        stdout.close()

        stdout_output = NULL_SEP.join(stdout_output)

        if not stderr.closed:
            stderr_output = list()
            while True:
                data = stderr.read()
                if not data:
                    break
                stderr_output.append(data)
            stderr.close()

            if stderr_output:
                stderr_output = NULL_SEP.join(stderr_output)
                if PY3:
                    stderr_output = stderr_output.decode(sys.stderr.encoding)

        #pid, status = os.waitpid(p.pid, 0)
        status = p.wait()

        if status != 0:
            raise InvocationException(
                'Program terminated with status: %d. stderr follows: %s' % (
                    status, stderr_output))
        elif stderr_output:
            print(stderr_output)

        # For each of the image files...
        for img in self.shape_files:

            # remove it
            os.unlink(os.path.join(tmp_dir, os.path.basename(img)))

        os.unlink(tmp_name)

        return stdout_output